We present a multifractal analysis of Mount St. Helens seismic activity during 1980-2002. The sei... more We present a multifractal analysis of Mount St. Helens seismic activity during 1980-2002. The seismic time distribution is studied in relation to the eruptive activity, mainly marked by the 1980 major explosive eruptions and by the 1980-1986 dome building eruptions. The spectrum of the generalized fractal dimensions, i.e. D q vs q , extracted from the data , allows us to identify two main earthquake time-distribution patterns. The first one exhibits a multifractal clustering correlated to the intense seismic swarms of the dome building activity. The second one is characterized by an almost constant value of D q ≈ 1, as for a random uniform distribution. The time evolution of D q (for q=0,2), calculated on a fixed number of events window and at different depths, shows that the brittle mechanical response of the shallow layers to rapid magma intrusions, during the eruptive periods, is revealed by sharp changes, acting at a short time scale (order of days), and by the lowest values of D q (≈ 0.3). Conversely, for deeper earthquakes, characterized by intense seismic swarms, D q do not show obvious changes during the whole analyzed period, suggesting that the earthquakes, related to the deep magma supply system, are characterized by a minor degree of clustering, which is independent of the eruptive activity.
We present a multifractal analysis of Mount St. Helens seismic activity during 1980-2002. The sei... more We present a multifractal analysis of Mount St. Helens seismic activity during 1980-2002. The seismic time distribution is studied in relation to the eruptive activity, mainly marked by the 1980 major explosive eruptions and by the 1980-1986 dome building eruptions. The spectrum of the generalized fractal dimensions, i.e. D q vs q , extracted from the data , allows us to identify two main earthquake time-distribution patterns. The first one exhibits a multifractal clustering correlated to the intense seismic swarms of the dome building activity. The second one is characterized by an almost constant value of D q ≈ 1, as for a random uniform distribution. The time evolution of D q (for q=0,2), calculated on a fixed number of events window and at different depths, shows that the brittle mechanical response of the shallow layers to rapid magma intrusions, during the eruptive periods, is revealed by sharp changes, acting at a short time scale (order of days), and by the lowest values of D q ( ≈ 0.3). Conversely, for deeper earthquakes, characterized by intense seismic swarms, D q do not show obvious changes during the whole analyzed period, suggesting that the earthquakes, related to the deep magma supply system, are characterized by a minor degree of clustering, which is independent of the eruptive activity.
We investigate numerically the Self Organized Criticality (SOC) properties of the dissipative Ola... more We investigate numerically the Self Organized Criticality (SOC) properties of the dissipative Olami-Feder-Christensen model on small-world and scale-free networks. We find that the small-world OFC model exhibits self-organized criticality. Indeed, in this case we observe power law behavior of earthquakes size distribution with finite size scaling for the cut-off region. In the scale-free OFC model, instead, the strength of disorder hinders synchronization and does not allow to reach a critical state.
ABSTRACT An important challenge in quantum science is to fully understand the efficiency of energ... more ABSTRACT An important challenge in quantum science is to fully understand the efficiency of energy flow in networks. Here we present a simple and intuitive explanation for the intriguing observation that optimally efficient networks are not purely quantum, but are assisted by some interaction with a ‘noisy’ classical environment. By considering the system's dynamics in both the site-basis and the momentum-basis, we show that the effect of classical noise is to sustain a broad momentum distribution, countering the depletion of high mobility terms which occurs as energy exits from the network. This picture suggests that the optimal level of classical noise is reciprocally related to the linear dimension of the lattice; our numerical simulations verify this prediction to high accuracy for regular 1D and 2D networks over a range of sizes up to thousands of sites. This insight leads to the discovery that dramatic further improvements in performance occur when a driving field targets noise at the low mobility components. The simulation code which we wrote for this study has been made openly available at figshare4.
The results of the analysis of the data collected with the NEMO Phase-2 tower, deployed at 3500 m... more The results of the analysis of the data collected with the NEMO Phase-2 tower, deployed at 3500 m depth about 80 km off-shore Capo Passero (Italy), are presented.Čerenkov photons detected with the photomultipliers tubes were used to reconstruct the tracks of atmospheric muons. Their zenith-angle distribution was measured and the results compared with Monte Carlo simulations. An evaluation of the systematic effects due to uncertainties on environmental and detector parameters is also included. The associated depth intensity relation was evaluated and compared with previous measurements and theoretical predictions. With the present analysis, the muon depth intensity relation has been measured up to 13 km of water equivalent.
Multifractal analysis of Mt. S. Helens seismicity as an indicator for eruptive activity
... Vito Latora, Andrea Rapisarda Dipartimento di Fisica e Astronomia, Università di Catania, Via... more ... Vito Latora, Andrea Rapisarda Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 64, I-95123 Catania, Italy Stephen Malone Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA Abstract ...
Multifractal Analysis of MT. S. Helens Seismicity as a Quantitative Characterization of the Eruptive Activity
... Vito Latora, Andrea Rapisarda Dipartimento di Fisica e Astronomia, Università di Catania, Via... more ... Vito Latora, Andrea Rapisarda Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 64, I-95123 Catania, Italy Stephen Malone Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA Abstract ...
We study the effects of the topology on the Olami-Feder-Christensen (OFC) model, an earthquake mo... more We study the effects of the topology on the Olami-Feder-Christensen (OFC) model, an earthquake model of self-organized criticality. In particular, we consider a 2D square lattice and a random rewiring procedure with a parameter 0 < p < 1 that allows to tune the interaction graph, in a continuous way, from the initial local connectivity to a random graph. The main result is that the OFC model on a small-world topology exhibits self-organized criticality deep within the nonconservative regime, contrary to what happens in the nearest-neighbors model. The probability distribution for avalanche size obeys finite size scaling, with universal critical exponents in a wide range of values of the rewiring probability p. The pdf's cutoff can be fitted by a stretched exponential function with the stretching exponent approaching unity within the small-world region.
Quantum coherence, decoherence and entanglement in light harvesting complexes
... 12:39 PM12:51 PM. Preview Abstract. Authors: Martin Plenio (Imperial College London). Filipp... more ... 12:39 PM12:51 PM. Preview Abstract. Authors: Martin Plenio (Imperial College London). Filippo Caruso (Imperial College London). Alex Chin (University of Hertfordshire). Animesh Datta (Imperial College London). Susana Huelga (University of Hertfordshire). ...
Towards experimental verifications of the transport mechanisms in light-harvesting dynamics
ABSTRACT Recently, we identified the key mechanisms explaining the very- high efficiency and robu... more ABSTRACT Recently, we identified the key mechanisms explaining the very- high efficiency and robustness of excitation energy transfer in bacterial photosynthesis, finding that dephasing noise may remarkably enhance the capability of transmitting energy (classical/quantum information) in light-harvesting systems (in communication complex networks [Caruso et al., PRL 2010]), by opening up additional transport pathways and suppressing the ineffective ones. To verify the relevance of such mechanisms in the actual bio-molecular systems, we propose how to gain control over the light-harvesting dynamics by using quantum optimal control tools. In this way, by means of optimally shaped and `robust&#39; laser pulses, we can: i) faithfully prepare the photosystem in some specific initial state (local site or coherent superposition, e.g. quasi-dark and -bright states), and ii) probe efficiently the dynamics, under realistic experimental conditions, i.e. sample of randomly oriented light-harvesting complexes and extra laser constraints related to an experiment in progress. These results could allow us to more easily discriminate the different transport pathways, to characterize the environmental properties, and so enhance our comprehension of coherent processes in biological complexes.
We explore the feasibility of the coherent control of excitonic dynamics in lightharvesting compl... more We explore the feasibility of the coherent control of excitonic dynamics in lightharvesting complexes, analyzing the limits imposed by the open nature of these quantum systems. We establish feasible targets for phase and phase/amplitude control of the electronically excited state populations in the Fenna-Mathews-Olson (FMO) complex and analyze the robustness of this control with respect to orientational and energetic disorder, as well as the decoherence arising from coupling to the protein environment. We further present two possible routes to verification of the control target, with simulations for the FMO complex showing that steering of the excited state is experimentally verifiable either by extending excitonic coherence or by producing novel states in a pump-probe setup. Our results provide a first step toward coherent control of these complex biological quantum systems in an ultrafast spectroscopy setup.
It is known that more than 50 species use the Earth's magnetic field for orientation and navigati... more It is known that more than 50 species use the Earth's magnetic field for orientation and navigation. Intensive studies particularly behavior experiments with birds provide support for a chemical compass based on magnetically sensitive free radical reactions as a source of this sense. However, the fundamental question of how quantum coherence plays an essential role in such a chemical compass model of avian magnetoreception yet remains controversial. Here, we show that the essence of the chemical compass model can be understood in analogy to a quantum interferometer exploiting quantum coherence. Within the framework of quantum metrology, we quantify quantum coherence and demonstrate that it is a resource for chemical magnetoreception. Our results allow us to understand and predict how various factors can affect the performance of a chemical compass from the unique perspective of quantum coherence assisted metrology. This represents a crucial step to affirm avian magnetoreception as an example of quantum biology, which exhibits a direct connection between quantum coherence and biological function.
We present details on a physical realization, in a many-body Hamiltonian system, of the abstract ... more We present details on a physical realization, in a many-body Hamiltonian system, of the abstract probabilistic structure recently exhibited by Gell-Mann, Sato and one of us (C.T.), that the nonadditive entropy S q = k[1 − Trρ q ]/[q − 1] (ρ ≡ density matrix; S 1 = −kTrρ lnρ) can conform, for an anomalous value of q (i.e., q = 1), to the classical thermodynamical requirement for the entropy to be extensive. Moreover, we find that the entropic index q provides a tool to characterize both universal and nonuniversal aspects in quantum phase transitions (e.g., for a L-sized block of the Ising ferromagnetic chain at its T = 0 critical transverse field, we obtain lim L→∞ S √ 37−6 (L)/L = 3.56 ± 0.03). The present results suggest a new and powerful approach to measure entanglement in quantum many-body systems. At the light of these results, and similar ones for a d = 2 Bosonic system discussed by us elsewhere, we conjecture that, for blocks of linear size L of a large class of Fermionic and Bosonic d-dimensional many-body Hamiltonians with short-range interaction at T = 0, we have that the additive entropy S 1 (L) ∝ [L d−1 − 1]/(d − 1) (i.e., ln L for d = 1, and L d−1 for d > 1), hence it is not extensive, whereas, for anomalous values of the index q, we have that the nonadditive entropy S q (L) ∝ L d (∀d), i.e., it is extensive. The present discussion neatly illustrates that entropic additivity and entropic extensivity are quite different properties, even if they essentially coincide in the presence of short-range correlations.
Classical noise assists the flow of quantum energy bymomentum rejuvenation
ABSTRACT An important challenge in quantum science is to fully understand the efficiency of energ... more ABSTRACT An important challenge in quantum science is to fully understand the efficiency of energy flow in networks. Here we present a simple and intuitive explanation for the intriguing observation that optimally efficient networks are not purely quantum, but are assisted by some interaction with a `noisy&#39; classical environment. By considering the system&#39;s dynamics in both the site-basis and the momentum-basis, we show that the effect of classical noise is to sustain a broad momentum distribution, countering the depletion of high mobility terms which occurs as energy exits from the network. This picture predicts that the optimal level of classical noise is reciprocally related to the linear dimension of the lattice; our numerical simulations verify this prediction to high accuracy for regular 1D and 2D networks over a range of sizes up to thousands of sites. This insight leads to the discovery that dramatic further improvements in performance occur when a driving field targets noise at the low mobility components.
It is generally impossible to probe a quantum system without disturbing it. However, it is possib... more It is generally impossible to probe a quantum system without disturbing it. However, it is possible to exploit the back-action of quantum measurements and strong couplings to tailor and protect the coherent evolution of a quantum system. This is a profound and counterintuitive phenomenon known as quantum Zeno dynamics (QZD). Here we demonstrate QZD with a rubidium Bose-Einstein condensate in a five-level Hilbert space. We harness measurements and strong couplings to dynamically disconnect different groups of quantum states and constrain the atoms to coherently evolve inside a two-level subregion. In parallel to the foundational importance due to the realization of a dynamical superselection rule and the theory of quantum measurements, this is an important step forward in protecting and controlling quantum dynamics and, broadly speaking, quantum information processing.
Escaping from a complex maze, by exploring different paths with several decision-making branches ... more Escaping from a complex maze, by exploring different paths with several decision-making branches in order to reach the exit, has always been a very challenging and fascinating task. Wave field and quantum objects may explore a complex structure in parallel by interference effects, but without necessarily leading to more efficient transport. Here, inspired by recent observations in biological energy transport phenomena, we demonstrate how a quantum walker can efficiently reach the output of a maze by partially suppressing the presence of interference. In particular, we show theoretically an unprecedented improvement in transport efficiency for increasing maze size with respect to purely quantum and classical approaches. In addition, we investigate experimentally these hybrid transport phenomena, by mapping the maze problem in an integrated waveguide array, probed by coherent light, hence successfully testing our theoretical results. These achievements may lead towards future bio-inspired photonics technologies for more efficient transport and computation.
Any physical process can be represented as a quantum channel mapping an initial state into a fina... more Any physical process can be represented as a quantum channel mapping an initial state into a final state. Hence it can be characterized from the point of view of communication theory. Recently a lot of efforts have been devoted to encompass memory effects within this approach. It is usually meant that memory effects arise when the application of a channel on several inputs is not merely the result of identical and independent maps. Alternatively, if the channel is defined by its infinitesimal generator in a continuous-time description, one refers as well to memory effects if such an evolution is non-Markovian. The consideration of such effects has given rise to more powerful tools than the traditional quantum channel approaches for describing quantum information processes. Moreover it constitutes a fertile ground where interesting novel phenomena emerge at the intersection of quantum information theory with other branches of physics. Recent developments in the field of quantum channels and memory effects are here reviewed. PACS numbers: 03.67.-a, 89.70.-a, 02.50.-r A. Discrete memory channels 23 B. Continuous memory channels 26 VIII. Quantum channels from dynamics with memory 30 A. Non Markovian master equations 32 B. Legitimate memory kernels 32 C. Markovian vs non-Markovian dynamics 33 D. A solvable model 34 IX. Summary and Outlook 34 Acknowledgments 35 A. Tools for characterizing quantum channels 35 B. Entropic quantities 36 arXiv:1207.5435v3 [quant-ph] 20 Nov 2012 C. Decomposition for non-anticipatory quantum channels 37 D. C * -and Quasi-Local Algebras 37 References 38
Uploads
Papers by Filippo Caruso